Variable resistor



Jan. 23, 1962 w. 'r. HARDISON ETAL 3,018,459

VARIABLE RESISTOR Filed June 7, 1960 l V/Lawe I HA [QB/501V,

WARREN 0 HUL BERT INVENTORS ing bracket 15,

atent VARIABLE RESISTOR Wilbur T. Hardison and Warren D. Hulbert,Riverside, Califi, assignors to Bourns, Inc., Riverside, Califi, acorporation of California Filed June 7, 1960, Ser. No. 34,394 Claims.(Cl. 338-180) The present invention relates to variable resistors, whichterm includes otentiometers.

The primary object of the present invention is to provide a variableresistor of the type wherein a movable contact is shifted lengthwisealong a resistance element by means of a rotatable leadscrew, whichvariable resistor can be mounted on the back side of a panel with just athreaded stud projecting through a hole in the panel, and with meansexposed at the front side of the panel for adjusting the leadscrew.

Another object of theinvention is to provide means for adapting avariable resistor of the type which is normally mounted on a pair ofparallel rods extending through tubular rivets in the body, so that thesaid variable resistor can be mounted on the back side of a panel with aslotted adjustment head projecting through the panel to enable thevariable resistor to be adjusted from the front side of the panel.

These and other objects and advantages of the invention will becomeapparent to those skilled in the art upon consideration of the followingdetailed description of the preferred embodiment thereof, referencebeing had to the accompanying drawings, wherein:

FIGURE 1 is a perspective view of a leadscrew-adjusted potentiometerembodying the principles of the invention;

FIGURE 2 is a top plan view of the same;

FIGURE 3 is a sectional view, taken at 3-3 in FIG- URE 2; and

FIGURE 4 is an enlarged fragmentary sectional view of the right hand endof the device as it is shown in FIGURE 3.

In the drawings, the reference numeral designates in its entirety apanel mount potentiometer of the leadscrewadjusted variety shown inPatent No. 2,777,926, to Marian E. Bourns. The potentiometer locomprises an elongated rectangular body 11, which is embraced on threesides by a channel-shaped sheet metal cover 12. The cover 12 is securedto the body by two tubular rivets 13 which pass through the sides of thecover 12 and through the body 11 near respective ends thereof. Therivets 13 also pass through aligned holes in the sides 14 of a U-shapedmountand the said rivets are headed over to secure the bracket sides 14to the potentiometer body.

The body 11 is preferably molded of, dielectric plastic material, and isformed with a central base portion 16 and upstanding end portions 17 and18. Mounted side by side in parallel grooves in the base portion 16 area resistance element 20 and a conductor strip (not shown). The ends ofthe resistance element 20 and the conductor strip are connected torespective ones of terminal wires 21 which pass through a hole 22 in theend 17 of the body.

Journa-led at its ends in the end portions 17 and 18, and

extending over the resistance element 20 and conductor strip, parallelthereto, is a leadscrew 23, one end of which projects through to theoutside and is provided with a head 24 that is slotted diametrically at25 to receive a screwdriver or the like for adjusting purposes. Theleadscrew 23 is held against longitudinal movement by a pin 26 which isinserted through a transverse hole in the body and engages acircumferential groove 27 in the leadscrew. A slider 30 embraces theleadscrew 23 and is operatively engaged by the threads thereof so thatthe slider is moved longitudinally of the leadscrew when the latter isturned, The slider 30 is prevented from turning with the lead screw bymeans of two runners 31 (only one of which can be seen in FIGURE 3),that extend downwardly from the slider at opposite sides thereof andslidably engage the edges of the central portion 16. Mounted on thebottom of the slider is a sheet metal contact member 32, having twolaterally spaced resilient fingers 33, only one of which can be seen inFIGURE 3. The two fingers 33 wipe on the resistance element 20 and onthe conductor strip, to make electrical contact therewith.

Normally, the potentiometer 10 is mounted on a pair of parallel screwsor rods (not shown) which are passed through the hollow rivets 13.However, there are situations where it is desirable to mount thepotentiometer on the back side of an instrument panel, with only theslotted head of the leadscrew exposed on the front side of the panel foradjustment purposes. To enable the potentiometer 10 to be mounted inthis manner on a panel P (FIGURE 3), the bracket 15 is provided withmeans extending through a hole 34, in the panel for securing thepotentiometer thereto and for adjusting the leadscrew.

As mentioned earlier, the bracket 15 is U-shaped in configuration, withsides 14 extending along the sides of the potentiometer body and securedthereto by rivets 13. The bracket sides 14 are connected by a bightportion 38 which is arched upwardly so that the center line of theleadscrew is disposed approximately between the top and bottom edges ofthe bracket. The bight portion 38 is apertured at 37, and a stud 36 isinsertedthrough the aperture from the inside of the bracket. Theaperture 37 is non-round, and preferably flat on two opposite sidesthereof; the stud 36 being correspondingly shaped so that it fits snuglywithin the aperture and is thus prevented from turning with respect tothe bracket. The stud 36 is provided at one end with a radial flange 39which bears against the inside of the bight portion 38, and is clampedthereby against the end of the potentiometer body 11. Formed within thestud is a central bore 40' of a diameter to receive the leadscrew head24, and this bore is joined by an annular shoulder 41 with an extensionbore 42 of somewhat smaller diameter, which extends through to theright-hand end of the stud. The outer end of the stud is threadedexternally at 43 to receive a mounting nut 44.

Rotatably disposed within the bore 42 is a cylindrical adjustment headmember 46 having a radial flange 47 at one end extending behind andseating against the shoulder 41. Projecting from the left-hand end ofthe member 46 is a diametrically extending tongue 48 which seats in theslot 25 of the leadscrew head 24. The member 46 is provided with acircumferential groove 50, in which is seated an O-ring 51 ofelastomeric material. The O-ring 51 provides a slight amount offrictional drag on the member 46 and also seals the clearance betweenthe member 46 and the stud to prevent the entrance of dirt or moisture.The outer end of the member 46 is slotted transversely at 52 to receivea screwdriver or other adjusting tool.

The potentiometer 10 is mounted on back side of the panel P by insertingthe stud 36 through the hole 34, and then screwing a nut 44 on thethreads 43. A look washer 53 is preferably interposed between the nut 44and the panel P so as to prevent the nut from loosening. With thepotentiometer thus mounted on the panel, adjustment of the leadscrew iseffected by merely turning the head member 46 with a screwdriver, theleadscrew being turned with the member 46 by the tongue 48 which isseated in the slot 25.

The bracket 15 with the stud 38 and associated parts may be assembledwith the potentiometer at the time of manufacture to make a panel mounttype of instrument. Alternatively, the bracket 15 and stud 38 may besold separately and later assembled to a standard potentiometer bymerely removing the rivets 13, placing the bracket sides 14- over thesides of the potentiometer body, and securing the bracket to the bodywith new tubular rivets.

While we have shown and described in considerable detail what we believeto be the preferred form of our invention, it will be understood bythose skilled in the art that various changes may be made in the shapeand arrangement of the several parts without departing from the broadscope of the invention as defined in the appended claims.

We claim:

1. A variable resistor adapted for mounting on the back side of a panelwith adjusting means projecting through an aperture in the panel to thefront side thereof, comprising an elongate leadscrew-actuatedpotentiometer having an elongate body and having an adjusting leadscrewhead projecting from one end of the body; a U-shaped mounting brackethaving opposed elongate limbs attached to said body and a bight portionextend ing across the said one end of the body; an externally threadedstud secured to said bracket and projecting therefrom substantiallycoaxially with said leadscrew head, said stud having a central bore intowhich said leadscrew head projects; a member rotatably disposed withinsaid bore and having a driving engagement at one end there of with saidleadscrew head, said member having its other end exposed for engagementby an adjusting tool; and a mounting nut cooperating with the thread ofsaid stud.

2. For mounting an elongate leadscrew-adjusted variable resistor on theback side of a panel with adjusting means thereof projecting through anaperture in the panel to the front side thereof, said variable resistorhaving a longitudinally extending leadscrew and an elongate body ofrectangular configuration with at least one fastening member extendingtransversely through said body from one side thereof to the other, saidleadscrew including a head projecting from one end of said body,mounting means comprising: a mounting bracket, said mounting bracketbeing of U-shape and including elongate side portions extendinglongitudinally along opposite sides of said body and each side portionhaving an aperture therein through which said fastening member passes,an apertured bight portion interconnecting said side portions, and anexternally threaded stud secured to said bight portion and projectingoutwardly therefrom coaxial with said head, said stud having a centralbore into which said leadscrew head projects; a member rotatablydisposed Within said bore and having a driving engagement at one endthereof with said head, said member being retained within said stud andhaving its other end exposed for engagement by an adjusting tool; and amounting nut screwed onto the threads of said stud.

3. For mounting an elongate leadscrew-adjusted variable resistor on theback side of a panel with adjusting means thereof projecting through anaperture in the panel to the front side thereof, said variable resistorhaving a longitudinally extending leadscrew and an elongate body ofrectangular configuration, with at least one fastening member extendingtransversely through said body from one side thereof to the other, saidleadscrew including a head projecting from one end of said body,mounting means comprising: a mounting bracket, said mounting bracketbeing of elongate U-shape and including: opposed elongate side portionsextending longitudinally along opposite sides of said body and each sideportion having an aperture therein through which said fastening memberpasses, an apertured bight portion intercon'necting said side portionsand with the aperture in the bight arranged concentric with said head;an externally threaded stud inserted through the aperture in said bightportion, said stud having a radial flange arranged to be clamped againstsaid one end of said body by said bracket, and said stud having acentral bore into which said head projects; a member rotatably disposedwithin said bore and having a driving engagement at one end thereof withsaid head, said member being retained within said stud and having itsother end exposed for engagement by an adjusting tool; and a mountingnut screwed onto the threads of said stud.

4. Potentiometric means adapted for alternative mounting according toeither of differing modes, said means comprising: a leadscrew-actuatedpotentiometer comprising an elongate transversely perforate body and aleadscrew mounted therein and having an end accessible for actuation atone end of said body and said leadscrew being at said one end providedwith a driver-slot; a U- shaped mounting bracket comprising opposedelongate limbs interconnected by an apertured bight portion, said limbsbeing disposed alongside said elongate body and being secured thereto; aflanged tubular stud having a tubular portion and a flange disposed andmaintained between the body 'of said potentiometer and the bight portionof said bracket and there held captive by said bracket with the tubularportion of said stud extending through the aperture in the bight of thebracket; rotatable leadscrew-engaging driver means disposed in saidtubular portion and constructed and arranged to engage said driver slotand rotate the leadscrew incident to being rotated, said driver meanshaving in turn a driver slot; and means for securing said tubular studto a panel.

5. Potentiometric means, comprising, in combination:

first means, including an elongate leadscrew-adjusted potentiometer ofthe type having an elongate body having transversely extending mountingmeans and an elongate adjusting leadscrew disposed longitudinally ofsaid body, said leadscrew having a driving end exposed at one end ofsaid body;

second means, including a threaded tubular stud and cooperating meansthreaded on the stud for securing the stud to a panel; and

third means, comprising interconnecting means closely embracing saidtubular stud and said elongate body, said interconnecting latter meansbeing constructed and arranged to maintain the said stud and the saidbody in fixed relationship each to the other and with the axis of thesaid tubular stud substantially in alignment with the axis of the saidleadscrew with the driving end of said leadscrew facing the bore of saidtubular stud.

References Cited in the file of this patent UNITED STATES PATENTS2,358,991 Miller Sept. 26, 1944 2,371,159 Erb Mar. 13, 1945 2,458,314Straub et al. Jan. 4, 1949 2,776,356 Kling Jan. 1, 1957 2,777,924Youngbeck Jan. 15, 1957 2,777,926 Bourns Jan. 15, 1957 2,836,690 BarrMay 27, 1958

